The present invention relates to a data processing unit of a microprogram control system which deals with variable length data.
In a data processing unit of a microprogram control system, a data string of a given data length (variable length) stored in a memory area of the main memory may occasionally be required to be transferred to another memory area thereof. In this case, in a data processing unit where the length of the data string or an address of the main memory at which the data string is stored is designated in units of one byte, data to be processed is generally read/written in units of one byte. Therefore, the number of memory access operations for processing the accessed data string of a given length is increased thereby, decreasing processing speed.